1. Field of the Invention
The present invention relates to a method of manufacturing a connector for a flat cable which is applied to an electrical connection device which receives and transmits electrical signals between a rotary body connected to a steering wheel and a fixed body connected to a steering column in a steering mechanism of a vehicle, for example, a connector for a flat cable and an applying member for applying ultrasonic vibrations to be used for the method.
2. Description of Related Art
When a kind of an electrical connection device transmits signals from a flat cable wounded around a rotary body to an the outside by a connector, as a connection means between the flat cable and the connector there is used a connector for the flat cable which is connected to a tip portion of the flat cable.
Conventionally, a connector for a flat cable is composed as the following plural connector terminals are exposed on obverse surfaces and reverse surfaces and are insert molded in a first holder at a pitch equal to that between conductor portions of the flat cable plural bus bars are exposed on obverse surfaces and reverse surfaces and are insert molded in a second holder assembled to the first holder at a pitch equal to that between the conductor portions of the flat cable. The conductor portions of the flat cable are interposed between the plural connector terminals and the plural bus bars, and are collectively welded with the connector terminals and bus bars by ultrasonic welding, thereby being connected together.
In this case, the plural connector terminals are insert molded in the first holder so that are parallel to one another and are each separated therebetween by insulation walls which are integrally formed to the first holder.
In the ultrasonic welding, the conductor portions of the flat cable is set, and is positioned between the connector terminals and the bus bars. In this state, an anvil is putted under the connector terminals and an ultrasonic applying member which is to be inserted between the insulation walls is pressed on bus bars from upside. Ultrasonic energy is applied to them, and thus the connector terminals, the conductor portions of the flat cable and the bus bars are collectively welded by ultrasonic welding.
However, according to the conventional connector, a width of a contacting portion with a bus bar in the ultrasonic applying member is narrower than that of the bus bar, and if the ultrasonic applying member is off determined position relative to the bus bar, it cause connection strength to be degraded at the ultrasonic welding. Thus, a high work precision is required at the ultrasonic welding.
The connector terminals are insert molded in the first holder with neighboring insulation walls, the insulation walls ensure an insulating state of a circuit of each connector terminal. However, it is easy to appear a phenomenon that excessive resin of the insulation wall mounts on the connector terminal when forming the connector terminal, and the phenomenon causes connection strength to be degraded at the ultrasonic welding.
In view of the above, an object of the present invention is to provide a method of manufacturing a connector for a flat cable which has a high connection strength at a connection portion of a connector terminal and a flat cable without complicating a work at a ultrasonic welding, is obtained stablebly and thereby to improve a reliability, a connector for a flat cable, and an applying member for applying ultrasonic vibrations to be used for the same method.
From a first aspect of the present invention, there is provided a method of manufacturing a connector for a flat cable comprising the steps of: placing a first cable conductor portion on a first connector terminal; accommodating the first cable conductor portion in a pressing recessed portion formed to an applying member; and applying ultrasonic vibrations to and pressing the first cable conductor portion and the first connector terminal to be welded to each other.
Preferably, further comprising the steps of placing a second cable conductor portion on a second connector terminal spaced from the first connector terminal; accommodating the second cable conductor portion in a pressing recessed portion formed to an applying member; applying ultrasonic vibrations to and pressing the second cable conductor portion and the second connector terminal to be welded to each other; and inserting an insulation wall between the first connector terminal and the second connector terminal.
From a second aspect of the present invention, there is provided an applying member for applying ultrasonic vibrations used for manufacturing a connector for a flat cable. The applying member comprises a main body which has a pressing recessed portion which has a first side portion and a second side portion. The pressing recessed portion is deep to accommodate a cable conductor portion and has an opening wider than a connector terminal. The first side portion is to be interposed between a first connector terminal and a second connector terminal. The second side portion is to be interposed between the second connector terminal and a third connector terminal.
Preferably, the pressing recessed portion of the main body is deep to accommodate a bus bar to be placed on the cable conductor portion.
From a third aspect of the invention, there is provided a connector for a flat cable comprising: a first holder; a first connector terminal which is in the first holder and is welded to a first cable conductor portion by application of ultrasonic vibrations and pressing; a second connector terminal which is in the first holder, is spaced from the first connector terminal and is welded to a second cable conductor portion by application of ultrasonic vibrations and pressing; and a casing which is fixed to the first holder and has an insulation wall inserted between the first connector terminal and the second connector terminal.
Preferably, further comprising a second holder which is fixed to the first holder, and a bus bar which is in the second holder and is welded to the first cable conductor portion by application of ultrasonic vibrations and pressing.
In above-mentioned invention, the applying member for applying ultrasonic vibrations accommodates and arranges the bus bar and the cable conductor portion, and is placed at a proper welding position easily. Further, a connector terminal, the cable conductor portion and the bus bar are collectively welded to each other within a width of the connector terminal by application of ultrasonic vibrations and pressing.
Though the main body of the applying member has a pressing recessed portion wider than the connector terminal, the connector terminal has a neighboring space and is insert molded. Thus, there is no insulation wall, and a space to use the applying member is ensured. Both side portions of the pressing recessed portion correspond to spaces neighboring to the connector terminal, and thus the applying member is allowed to descend.
There is no insulation wall at a neighboring position of the connector terminal, and there disappear the phenomenon that resin mounts on the connector terminal due to an excessive resin of the insulation wall. Thus, connection strength is improved at ultrasonic welding and a connection portion in ultrasonic welding step is visually viewed.
Further, circuits of connector terminals are each separated by the insulation wall of the casing, and, with vibration stress to be supposed after a vehicle loads with the circuit, an insulating state between neighboring circuits is ensured.